The 49-year-old, who serves as an actor and producer on the movie, realises that the movie became "bogged down" in its initial political message, reported Digital Spy.
Pitt stars as Gerry Lane in the film, which sees a zombie pandemic break out across the world. He explained that he initially wanted to use the zombie plot to send a socio political message.
"At the time, I was really interested in a more political film, using the zombie trope as a kind of Trojan horse for asking, 'What would happen to socio political lines if there was a pandemic like this? Who would be on top? Who would be the powerful countries and who would be the most vulnerable?'
Despite the decision to edit out some of the more political scenes in the film, Pitt maintained that it is more than just a fantasy summer blockbuster.
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"These movies are very intricate puzzles, and you have to keep winding the mechanisms and then trigger them all at just the right time. We give so much more credence to the end-of-the-year dramas.
"In these movies you're triggering emotions, too - a thrill response - but they are far more calibrated. You've got to be a bit of a technician."